| 1. |
|
|
| 2. |
- Edfelt, Åsa, et al.
(författare)
-
Stratigraphy and tectonic setting of the host rocks to the Tjårrojåkka Fe-oxide Cu-Au deposits, Kiruna area, northern Sweden
- 2006
-
Ingår i: GFF. - : Taylor & Francis. - 1103-5897 .- 2000-0863. ; 128:3, s. 221-232
-
Tidskriftsartikel (refereegranskat)abstract
- The Tjårrojåkka area is located about 50 km WSW of Kiruna, northern Sweden, and hosts one of the best examples of spatially and possibly genetically related Fe-oxide and Cu-Au occurrences in the area. The bedrock is dominated by intermediate and basic extrusive and intrusive rocks. An andesite constrains the ages of these rocks with a U-Pb LA-ICPMS age of 1878±7 Ma. They are cut by dolerites, which acted as feeder dykes for the overlying basalts. Based on geochemistry and the obtained age the andesites and basaltic andesites can be correlated with the 1.9 Ga intermediate volcanic rocks of the Svecofennian Porphyrite Group in northern Sweden. They formed during subduction-related magmatism in a volcanic arc environment on the Archaean continental margin above the Kiruna Greenstone Group. Chemically the basalts and associated dolerites have the same signature, but cannot directly be related to any known basaltic unit in northern Sweden. The basalts show only minor contamination of continental crust and may represent a local extensional event in a subaquatic back arc setting with extrusion of mantle derived magma. The intrusive rocks range from gabbro to quartz-monzodiorite in composition. The area is metamorphosed at epidote-amphibolite facies and has been affected by scapolite, K-feldspar, epidote, and albite alteration that is more intense in the vicinity of deformation zones and mineral deposits. Three events of deformation have been distinguished in the area. D1 brittle-ductile deformation created NE-SW-striking steep foliation corresponding with the strike of the Tjårrojåkka-Fe and Cu deposits and was followed by the development of an E-W deformation zone (D2). A compressional event (D3), possible involving thrusting from the SW, produced folds in the central part of the area and a NNW-SSE striking deformation zone in NE.
|
|
| 3. |
- Kemp, Tony, et al.
(författare)
-
Concurrent Pb-Hf isotope analysis of zircon by laser ablation multi-collector ICP-MS, with implications for the crustal evolution of Greenland and the Himalayas
- 2009
-
Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541. ; 261:3-4, s. 244-260
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedThe in situ Lu-Hf isotope analysis of zircon by laser ablation has emerged as a high-calibre tool for tackling magmatic and crustal evolution. The strength of the approach lies with the ability to target specific zircon growth domains identified by imaging, and thus to unravel polyphase crystallisation histories. However, due to the volume of material being sampled during analysis there remains the possibility of ablation-induced mixing between Hf from domains of different age. Inaccurate Hf isotope ratios and spurious geological interpretations could result. One approach to this problem involves dating the same volume of material analysed for Hf isotopes by concurrently measuring (207)Pb/(206)Pb ratios during ablation [Woodhead,J.D., Hergt,J.M.. Shelley, M., Eggins, S., Kemp, R. 2004. Zircon Hf-isotope analysis with an excimer laser, depth profiling, ablation of complex geometries, and concomitant age estimation. Chemical Geology 209,121-135.]. This paper explores the viability of this dual analysis by investigating complex zircons from three different geological contexts, detrital zircons in sedimentary rocks, inherited zircons in granites, and zircons in metamorphosed Eo-Archaean TTG gneisses from Greenland. The implications of the Greenland data for Archaean crustal evolution are discussed in the light of published solution zircon Hf isotope datasets from these gneisses. A case study of detrital zircons from modern river sands in the Himalayas highlights the potential of the technique for providing a rapid, cost-effective picture of crustal evolution that should complement regional bulk rock studies.
|
|
| 4. |
- Kolzenburg, Regina, et al.
(författare)
-
Structural integrity and skeletal trace elements in intertidal coralline algae across the Northeast Atlantic reveal a distinct separation of the leading and the trailing edge populations
- 2023
-
Ingår i: Marine Environmental Research. - : Elsevier. - 0141-1136 .- 1879-0291. ; 190
-
Tidskriftsartikel (refereegranskat)abstract
- Intertidal macroalgae, such as coralline algae, represent an essential structural element and substrate in rocky coastal zones. They have a high degree of flexibility allowing their survival in environments with severe mechanical stress during tidal cycles. This study characterised the genicula and intergenicula of the calcifying red algae Corallina officinalis across its geographic distribution in the Northeast Atlantic. Poleward populations have constructed more sturdy cell walls compared to equatorward populations, potentially due to greater local adaptations to higher frequency and intensity of environmental factors like storms and wave action. Southern populations showed a lack of local adaptation culminating in survival rather than thriving within their current environment, hence, they are located at the margin of this species' favourable conditions. Results clarify significant differences between latitudes and indicate a north-to-south gradient in this species’ skeletal elemental composition. Northern populations were dominated by cadmium, whereas chromium was the major trace element found in southern populations. In the future, these characteristics could lead to a permanent decline and a decrease in the ecosystem functions of C. officinalis in the southern locations in the Northeast Atlantic, which may be accelerated by predicted future climatic changes.
|
|
| 5. |
|
|
| 6. |
|
|
